In the context of this description, the gearshift to which particular reference is made is the rear one, which moves the chain among the different sprockets of the sprocket assembly associated with the rear wheel of the bicycle.
The movement of the chain is typically actuated through the movement of a derailleur associated with an actuation linkage associated with the frame of the bicycle at the rear wheel.
The bicycle gearshift can be mechanically actuated or motorized. In the first case the movement of the derailleur is carried out by using a sheathed cable (so-called Bowden cable). In the second case the movement of the derailleur is carried out by using a drive member that is properly driven, typically electrically. The action exerted on the actuation linkage by the sheathed cable or by the drive member causes the deformation of the actuation linkage and, consequently, the movement of the derailleur.
The actuation linkage typically comprises a first body configured to be rotatably connected to the bicycle frame, a second body configured to support the derailleur and a pair of articulation rods that connect the first body and the second body.
Rear gearshifts provided with locking means of the gearshift in order to facilitate the dismounting/remounting of the rear wheel (for example in the case of a puncture to the tire of the rear wheel) are known. Such locking devices lock the gearshift in a pulled-back position with respect to the position occupied in the normal operation operative condition of the gearshift. This makes it possible to move the upper pulley of the derailleur of the gearshift into a position such as not to obstruct the dismounting and remounting of the rear wheel of the bicycle from/onto the bicycle frame.
EP 1902936 describes a locking device of a bicycle gearshift that is arranged between a connection member of the actuation linkage to the bicycle frame and the first body of the actuation linkage. The connection member is fixed to the frame through an attachment screw, whereas the first body is rotatably connected to the connection member at a rotation axis and moves between an unlocked position of the gearshift and a locked position of the gearshift, such positions being angularly spaced. The locking device is configured to selectively hold the first body in the locked position and comprises a first pin which acts on a spring housed in a blind cavity of the first body, wherein when the first body is in the locked position the spring is in a preloaded state and pushes the first pin in a recess formed in the connection member. Such a recess is defined in a stepped through hole formed in the connection member. A second pin is mounted in such a stepped through hole, said second pin comprising an actuation end portion that projects from the connection member on the opposite side with respect to the first body. The second pin is actuated to push the first pin outside of the recess, so as to be able to rotate the first body with respect to the connection member, bringing it into the unlocked position.
The Applicant has observed that the locking device of the bicycle gearshift described in the aforementioned prior art document needs two distinct cavities (blind cavity in the first body and stepped through hole in the connection member) in which two distinct pins (first pin and second pin) slide. This results in a constructive and structural complication. Furthermore, the two cavities, being exposed to the outside, can be receptacles of dirt or water, with the risk of compromising the correct operation of the locking device.
The problem at the basis of the present invention is to provide a bicycle gearshift comprising a locking device that is constructively simpler and more reliable than the one described above with reference to the prior art.